The present invention relates to devices for transmitting and diffusing light energy at cancerous tumors to activate light sensitive drugs.
Various forms of cancer constitute the second leading cause of death in this country. For decades medical research has groped for a still elusive treatment that would cure cancer in its many forms or prevent its inception. Both government and private funds have enabled researchers to devolve more effective drug treatment regimens for certain cancers. Surgery, drugs, chemotherapy and radiation, individually or in combination, are preferred treatment procedures.
However, each of these approaches has some drawbacks. Surgical techniques cannot insure complete removal of malignant tumors, particularly those that have begun to metastasize. In their efforts to eradicate every vestige of cancerous growth, surgeons are often criticized for removing too much "good" tissue. Drugs have contraindications for their use, and individuals may exhibit different adverse reactions to them. Chemotherapy and radiation treatments often result in loss of appetite, weight and hair. Thus, while only certain portions of the body are treated, the whole body is often drastically affected.
To eliminate problems associated with such treatment procedures, innovative researchers designed what have come to be known as "magic bullet" treatment approaches. In such a treatment, a "magic bullet" is directed to a particular cancerous site within a body and exerts its effects only within that limited area. The body as a whole is not affected. Examples of such approaches are drug-filled, antibody-tagged red blood cell "ghosts" and drug-tagged monoclonal antibodies. Both the antibodies and red cell "ghosts" attach directly to tumor cells and release anti-carcinogenic drugs only at that site.
Another example of a "magic bullet" approach is photodynamic therapy (PDT). PDT relies on principles of photochemistry in which light of a specific wavelength and energy acts as a catalyst promoting certain chemical processes within a living cell. Common photochemical reactions encountered daily include those associated with vision and photosynthesis. Researchers used their knowledge of photochemical processes to devise the unique treatment therapy termed PDT.
In PDT, a patient is injected with a mixture of chemicals, for example, "hematoporphyrin derivative" ("HpD"). HpD is extracted from blood serum and is known to lodge preferentially within cancer cells. It remains within these cancer cells at a higher concentration than found in normal cells at 48-72 hours after injection. Subsequent exposure of drug-treated cells to light of specific energy level (chosen by a physician with respect to tumor nature and location) and wavelength (usually 630 nanometer, red light) results in death of the cancer cells without harm to surrounding normal, healthy tissue. While the specific reaction sequence leading to cell death is not fully understood, the phenomenon is well-known and increasingly used in cancer treatments. Patients must refrain from exposure to sunlight for several weeks after treatment since their sensitivity to light remains high during this time. No other side effects are known to accompany HpD treatment.
U.S. Pat. Nos. 4693556 and 4660925, both to McCaughan, describe devices for transmitting and diffusing light to various areas within the body. In these body areas, transmitted light energy activates photosensitive drug reactions (PDT). A tumor's location within the body dictates which of McCaughan's two inventions should be used for treatment. One version of the device has a spherical terminus for treating cavitary-area cancers like bladder tumors; the other version (shown in FIG. 5 of the present invention) has a cylindrical terminus with a flat distal end for treating tubular-area cancers such as esophageal cancers.
McCaughan's devices have inherent structural limitations in that neither one is able to penetrate and lodge within a tumor mass. Likewise, neither of these devices is appropriate for use where blood vessels or nerves, which may be adversely affected by intense light energy, traverse a tumor mass. Neither device has a shield to deflect light and thereby prevent destructive light energy from reaching beyond their light-emitting tips. A further limitation exists in the manufacture of McCaughan's light-dispersing devices. It requires a procedure involving successive layering of an epoxy-quartz mixture onto an optical fiber, which is costly in terms of both time and labor.
Accordingly, it is the general object of the present invention to provide an improved laser catheter diffuser that overcomes the problems of the prior art.
It is another object of this invention to provide an improved laser catheter diffuser capable of penetrating a malignant tumor mass, while simultaneously shielding certain areas within or adjacent to the tumor mass from harmful light radiation.
It is another object of this invention to provide a laser catheter diffuser that reflects and diffuses light to the greatest extent possible, thereby providing a maximum amount of light energy for activation of photochemical reactions in a drug activation cycle.
It is yet another object of this invention to provide a laser catheter diffuser that decreases time and cost factors associated with its manufacture.
The above and other objects and advantages of this invention will become more readily apparent when the following description is read in conjunction with the accompanying drawings.